Generally, none. We don't recommend digging holes because they'll be too big or too small and fill up with water. Holes can also be a Health and Safety problem ie trip hazard. They won't need manure applying either. The only thing we do recommend is Root grow, which seems to work pretty well, or bone meal.
Hi - If you are grafting onto an existing tree in the garden, then you can wait until just before budbreak. If you do it earlier you stand a chance of the wind or birds or snow from dislodging the graft joint.
However if it is more controlled, and grafting onto barerooted rootstock or even potted rootstock. You can graft anytime from Christmas to bud break. These have to be grown in bird proof and dog proof etc areas, typically in the greenhouse or even the back of the garage. Ensure soil and roots kept damp. Then put outside come spring.
When planting, any dwarfing or semi dwarfing trees will need a stake for support all their life. Any non dwarfing trees only need temporary canes. Do not forget to use a rabbit or vermin guard if necessary.
Weeds compete with young trees for water and nutrients. A weed-free zone should be established at the base of the tree that extends out to form a circle with a diameter of 1 metre. Mulch, herbicide or cultivation may be used to prevent weeds.